Graphene is a two-dimensional material with remarkable optical, thermal, and electrical properties. Graphene is a single-atom layer that can absorb incident light rays in a broad band range of frequencies through interband and intraband transitions. The interband transitions dominate infrared (IR) and visible light absorption, while intraband transitions govern terahertz (THz) detection. Based on the interband and intraband transitions, different types of graphene-based detectors may be developed that are capable of working at different wavelengths.
Graphene is capable of detecting W-band of the microwave part of the electromagnetic spectrum and THz radiation at room temperature. W-band ranges from 75 to 200 GHz and THz radiation includes electromagnetic waves within a band of frequencies from 0.1 THz to 10 THz. THz radiation occupies a range of electromagnetic spectrum between microwaves and infrared light waves, which is known as the THz gap. The frequency of electromagnetic radiation in the THz gap becomes too high to be measured digitally via conventional electronic counters.
Different devices have been developed that take advantage of peculiar photo detection properties of graphene in W-band and THz regions. For example, graphene field effect transistors (FETs), graphene P-I-N junctions, plasmonic graphene-nanoribbon FETs, graphene-THz modulators, and zero-bias graphene-FETs are among the devices developed for detecting W-band and THz radiations at room temperature.
Although these graphene devices are capable of working at room temperature, technical issues include considerably lower efficiency than conventional cooled bolometers. In addition, such devices structures are relatively complex. For example, graphene-FETs have been used as THz detectors, but their structures are complex and their manufacturing process involves costly electron beam lithography. Other technical issues with conventional graphene-based THz detector devices include small effective photo detection area and short carrier life time.
There is therefore a need in the art for simple and cost effective graphene-based detectors that are capable of working at room temperature with an efficiency equal or higher than conventional superconductor-based detectors, such as cooled bolometers. There is a further need in the art for graphene-based detectors that are manufactured through simple manufacturing processes.